The present invention is directed to a door lock guard for prohibiting forced entry and, more particularly, a door guard for protecting the cylinder of a door lock.
In recent years there has been a significant increase in the number of burglaries and forced entries being perpetrated. There are a number of sophisticated burglar alarm systems available which detect unlawful entry and sound a warning. While these known systems are quite reliable and effective they generally are fairly expensive to purchase and install thus making them beyond the financial reach of the majority of individuals. Naturally, it would be highly desirable to provide a device for prohibiting forced entry which is inexpensive to manufacture and simple to install.
Devices which protect the latch bolt of door locks from forcible retraction are known in the art. These devices are comparatively inexpensive and comprise a member which shields the latch bolt whereby it cannot be engaged by a "tool" inserted between the door and doorjamb. Such prior mechanical safety devices, however, do not prevent unauthorized access obtained by forced rotation of the lock cylinder. The lock cylinder is typically threaded into the lock and subsequently restrained against rotation by a single set screw which is inserted in the lock face plate from the door end. In most installations a sufficient portion of the cylinder extends from the surface of the door to permit the gripping thereof with a jaw-type tool. Twisting of the cylinder will result in bending the set screw whereupon the cylinder may be unscrewed sufficiently to open the lock. Decorative plates which are sometimes placed about the protruding cylinder are easily crushed and thus do not alleviate the problem.
Accordingly, it is the principal object of the present invention to provide a door guard for prohibiting forced entry.
It is a particular object of the present invention to provide a door guard for protecting the cylinder of a door lock from forced entry.
It is a further object of the present invention to provide a door guard for prohibiting forced entry which is inexpensive to manufacture and easy to install.
Further objects and advantages of the present invention will appear below.